Minors’ mental health is a subject of high global concern. Understanding the factors that influence their mental health is essential to improving the health of future generations. In this study, an analysis of the Strengths and Difficulties Questionnaire’s usefulness is carried out, as a validated tool, recognized in Spain and internationally, for the measurement of minors’ mental health. In turn, the influence of the variables of gender, age, and physical health, along with the occupational social class of parents on Spanish minors’ mental health, has been analyzed. Spanish minors with good physical health and of parents with middle and higher education, as well as in an occupational social class, are less likely to suffer mental health problems. On the other hand, it seems that internalizing symptoms are more likely in girls, and externalizing symptoms are more likely in boys. However, when a global measure of mental health is made without specific subscales, the effects of gender and age diverge greatly, according to the studies. Although there are examples of current research using the same measurement tool, there is still a need for many more international studies that are coordinated using the same methodology. This study identifies the factors which the international and Spanish scientific literature has revealed as being determinants in minors’ mental health. Finally, it is essential that the influence of these factors be assessed in the areas of primary care and mental health to facilitate better detection, intervention, or prevention of mental health problems in today’s children, as well as the children of future generations.